Fault tolerance is the object of prolonged endeavor in aircraft design. A high degree of fault tolerance can be achieved by providing for redundancy in controlled devices, as well as in the associated control circuits. Many failure modes may be detected by monitoring various signals. Knowing what to monitor and when to shutdown a particular control channel is a key concern. This is especially poignant in the context of aircraft design wherein nondetection of a failure and/or nuisance failures can cause a rapid deterioration in handling characteristics. Weight, space and cost considerations favor increasing fault tolerance through the use of more electronics rather than more mechanical hardware.